[PATCH] D120328: [DAGCombine] insert_subvector undef, (splat X), N2 -> splat X

[Paul Walker via Phabricator via llvm-commits]

paulwalker-arm added a comment.

Hi @cameron.mcinally, I've finally had chance to circle back to this (no April fools joke I promise :) ) and looking at `DAGCombiner::visitINSERT_SUBVECTOR` I can see several instances where it throws away `undef` information, not least the first two combines before my new one. So my feeling is there's no expectation to preserve it for our use case either.


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https://reviews.llvm.org/D120328